Electric control circuit system for internal combustion engines

ABSTRACT

There is provided an electric control circuit system for internal combustion engines comprising an electric motor for controlling the number of revolutions of an internal combustion engine, a control resistor in the energizing circuit for the electric motor, a control resistor on-off cutout circuit, an AC generator for generating a speed voltage proportional to the number of revolutions of the engine, a relay control circuit for generating pulses having an on-off ratio corrsponding to the speed voltage, and an electric motor control relay, whereby when the diesel engine rotates at an excessive speed, the fuel injection quantity of a fuel injection system in the engine is reduced by the resistor on-off cutout circuit and the relay control circuit.

United States Patent [191 Hobo et a1.

[ Oct. 28, 1975 1 ELECTRIC CONTROL CIRCUIT SYSTEM FOR INTERNAL COMBUSTION ENGINES [75] Inventors: Nobuhito Hobo, lnuyama; Sumihiro Kaga, lnazawa, both of Japan [73] Assignee: Nippondenso Co., Ltd., Kariya,

Japan [22] Filed: Aug. 28, 1973 [21] Appl. No.: 392,349

[52] US. Cl. 123/102; 123/148 E; 123/103 R [51] Int. Cl. F02N 17/00 [58] Field of Search 123/102 [56] References Cited UNITED STATES PATENTS 3,182,648 5/1965 Schneider 123/148 Primary Examiner-Wendell E. Burns Assistant E.\'aminer.lames W. Cranson, Jr. Attorney, Agent, or FirmCushman, Darby & Cushman 57 ABSTRACT There is provided an electric control circuit system for internal combustion engines comprising an electric motor for controlling the number of revolutions of an internal combustion engine, a control resistor in the energizing circuit for the electric motor, a control resistor on-off cutout circuit, an AC generator for generating a speed voltage proportional to the number of revolutions of the engine, a relay control circuit for generating pulses having an on-off ratio corrsponding to the speed voltage, and an electric motor control relay, whereby when the diesel engine rotates at an excessive speed, the fuel injection quantity of a fuel injection system in the engine is reduced by the resistor on-off cutout circuit and the relay control circuit.

4 Claims, 4 Drawing Figures DRIVING g 6 MEANS T4 SPEED I 3 VOLTAGE l2 GENERATOR US. Patent Oct.28,1975 sheet 1 on 3,915,130

SPEED VOLTAGE GENERATOR *SPEED VOLTAGE E -ENG|NE RPM N FIG 4 964 I65 leoo led a I58 a- ELECTRIC CONTROL CIRCUIT SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric control circuit for an internal combustion engine, particularly a diesel engine, wherein when the speed of the diesel engine exceeds the normal maximum revolutions, a control element, such as, the control rack of a fuel injection pump controlled by a pneumatic governor or the throttle valve for regulating the pressure in the inlet manifold, is forcibly actuated to reduce the quantity of fuel delivered by a fuel injection pump with a pneu matic governor and thereby to prevent the overspeeding of the diesel engine.

2. Description of the Prior Art Known diesel engines of this type equipped with a fuel injection pump having a pneumatic governor have a disadvantage in that when the control characteristic of the pneumatic governor varies with a change in the atmospheric pressure, for example, there is the danger of the diesel engine being caused to overspeed and eventually damaged.

SUMMARY OF THE INVENTION With a view to overcoming the foregoing diffieulty, it is the object of the present invention to provide electric control circuit system for internal combustion engines wherein the number of revolutions of an engine is electrically detected, whereby when the engine revolutions exceed the normal maximum revolutions, a control element is actuated by an electric motor or the like to reduce the quantity of fuel delivered by a fuel injection pump and thereby to prevent the engine from overspeeding.

A great advantage of the present invention is hunting phenomenon of an internal combustion engine due to the use of an onoff control circuit and the breaking down of the engine due to its overspeeding can be prevented, thereby improving the efficiency of control of an engine by an engine controlling electric motor and ensuring a longer life for a control relay.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in greater detail with reference to the illustrated embodiments. The basic circuit construction of the system of this invention will be described first with reference to FIG. I in which numeral 1 designates a speed voltage generator for generating a speed voltage E corresponding to the number of revolutions N of a diesel engine as illustrated in FIG. 2, numeral 2 an error detecting transistor. numeral 3 a relay actuating transistor. Numeral 4 designates a comparator Zener diode, numeral 5 a feedback capacitor, numeral 6 a revolution setting potentiometer, numerals 7 and 9 resistors, numeral 8 a capacitor, numeral 10 a surge voltage absorbing diode. Numeral l2 designates a control unit, numeral 13 a reversing transfer relay, numeral 13a a relay coil, number 1312 a movable contact which is shifted from one fixed contact to the other by the electromagnetic attraction of the relay coil numerals 13a, 13p and 1311 fixed contacts. Numeral l4 designates a driving means whose one terminal 14d is connected to the fixed contact 13;) so that when the movable contact 13b comes into contact with the fixed contact 13p, the driving means I4 forcibly moves a control rack controlled by a pneujection pump when the movable contact 13b comes into contact with the fixed contact 1311. Terminals I1 and 16 are connected to the positive side of a DC power source.

With the construction described above. the operation of the basic circuit of this invention will now be described. The speed voltage generator I generates the DC speed voltage E corresponding to the revolutions N of the diesel engine as shown in FIG. 2. With the voltage driving ratio of the revolution setting potentiometer 6 preliminarily adjusted so that the voltage applied to the comparator Zener diode 4 when the revolutions of the diesel engine are greater than the maximum rev olutions at the normal engine speed is higher than the breakdown voltage of the Zener diode 4, if the revolutions of the diesel engine are lower than the maximum revolutions at the normal engine speed, the error de tecting transistor 2 is rendered nonconductive and the relay actuating transistor 3 is rendered conductive. As a result, the collector current of the relay actuating transistor 3 flows into the relay coil 13a of the reversing transfer relay 13. causing the movable contact 1317 to engage the fixed contact 1321.. In this case, if the cam switch 15 is inthe closed position, current flows to the driving means 14 through the terminal l4i so that the control element or the control rack of the fuel injection pump is operated in a direction that increases the quantity of fuel delivered by the fuel injection pump until the control element reaches its normal operating position. When the control element is eventually moved to the normal operating position thereof, the cam switch 15 is opened with the result that the operation of the driving means 14 is stopped to cause the pneumatic governor to control the quantity of fuel delivered by the fuel injection pump. This pneumatic governor is of conventional type and therefore its construction and operation will not be described in detail.

When the number of revolutions of the diesel engine exceeds the maximum revolutions at the normal speed. the speed voltage generated by the speed voltage generator 1 becomes higher than the breakdown voltage of the comparator Zener diode 4 so that the base current flows in the error detecting transistor 2 to cause conduction between the collector and the emitter thereof. At this instant, the charge that has been stored in the capacitor 8 through the terminal 11, the resistor 7, the capacitor 8, the base and the emitter of the relay actuating transistor 3 and the ground. applies a reverse bias to the relay actuating transistor 3 to render the relay actuating transistor 3 nonconductive. This cuts off the supply of the exciting current to the relay coil 13a of the reversing transfer relay 13 and thus the movable contact 1317 comes into contact with the fixed contact 1312. Consequently. current flows to the driving means 14 through the terminal 14d to operate the control element in the direction which decreases the quantity of fuel delivered by the fuel injection pump. During this time interval. the capacitor 8 is charged in the reverse direction by the current flowing through the terminal 11, the resistor 9, the capacitor 8, the collector and the emitter of the error detecting transistor 2 and the ground. As a result. the reverse bias voltage applied to the base of the relay actuating transistor 3 is gradually reduced so that the base of the relay actuating transistor 3 is eventually biased in the forward direction. At this instant. conduction is caused between the collector and the emitter of the relay actuating transistor 3 and thus current flows into the relay coil 13a of the reversing transfer relay 13 causing the movable contact 131) to come into contact with the fixed contact 1311. Consequently, the potential at the collector of the relay actuating transistor 3 decreases and thus the voltage between points P and is decreased by the charge previously stored in the feedback capacitor 5 through the terminal 11, the relay coil 13a. the capacitor 5, the revolution setting potentiometer 6 and the ground. This stops the base current of the error detecting transistor 2 supplied through the comparator Zener diode 4 and therefore the error detecting transistor 2 is rendered nonconductive. When this happens. the feedback capacitor 5 is charged in the reverse direction by the current caused by the speed voltage generated by the speed voltage generator 1 and flowing through the collector and the emitter of the relay actuating transistor 3. Consequently. the voltage between the points P and e begins to gradually rise and it again becomes higher than the breakdown voltage of the comparator Zener diode 4, whereupon the error detecting transistor 2 is again rendered conductive and thus the relay actuating transistor 3 is rendered nonconductive. Thereafter, this process of the conduction and nonconduction of the error detecting transistor 2 and the relay actuating transistor 3 is repeated in this manner to thereby cause and sustain oscillations in this system. In this case, the ratio ofthe conduction time to the nonconduction time of the relay actuating transistor 3 varies in accordance with the time interval during which the feedback capacitor 5 is charged by the speed voltage generator 1 and this capacitor voltage becomes higher than the breakdown voltage of the comparator zener diode 4, that is. the difference between the revolutions of the diesel engine and its maximum normal revolutions. Accordingly, the conduction time of the relay actuating transistor 3 is decreased in proportion to the extent by which the revolutions of the diesel engine are greater than its maximum normal revolutions, so that the movable contact 13b of the reversing transfer relay 13 remains in contact with the fixed contact 13p longer than the time interval which it remains in contact with the fixed contact 1311 and therefore the effective value of the current that flows through the terminal 14d becomes greater than the effective value of the current that flows through the terminal 141'. In this manner. the control element or the control rack of the fuel injection pump is forcibly operated by the driving means 14 to reduce the quantity of fuel delivered. thereby controlling the number of revolutions of the diesel engine to always operate the engine at a speed lower than the maximum normal revolutions and thus to prevent the overspeeding of the engine.

Next, the basic electric circuit of this invention shown in FIG. 1 will be described in greater detail with reference to an exemplary electric circuit of FIG. 3 showing a first embodiment of this invention. In FIG. 3. numeral 40 designates a key switch including an starting terminal 40a which is closed when the engine is started and an operating terminal 4012 which is closed when the engine is in operation. Numeral 50 designates a speed detector consisting of a generator which generates an AC voltage corresponding to the engine speed, numeral 60 a reversal detector which is energized when the direction of rotation of the running engine is reversed. Numeral designates a control resistor, numeral a battery. numeral 30 a driving control unit comprising an internal combustion engine controlling electric motor 31 and a switch mechanism 32 comprising four contacts 33, 34, 35 and 36 and two cam switches 37 and 38 actuated by the controlling electric motor 31 to selectively close the contacts 33, 34, 35 and 36. Numeral 20 designates a control relay unit comprising two relays 21 and 22. The relay 2] comprises a relay coil 21a, a movable contact 21b which is shifted from one fixed contact to the other by the electromagnetic attraction of the coil 21a, fixed contacts 21p and 21a and are extinguishing capacitors 23 and 24, while the relay 22 comprises a relay coil 22a, mov able contacts 22b and 220 which are actuated in associated relation by the electromagnetic attraction of the relay coil 22a. fixed contacts 22p, 22" and 22g, and are extinguishing capacitors 25, 26 and 27. Numeral designates a comparator control circuit comprising a starting relay 190, a relay control circuit 101 and a resistor cutout circuit 102. The relay 190 comprises a relay coil 19011, a movable contact which is shifted from one fixed contact to the other by the electromagnetic attraction of the relay coil 190a, and fixed contacts 190p and 190. The relay control circuit 101 comprises a full-wave rectifier 111 for converting the AC voltage generated by the speed detector 50 into a DC voltage, smoothing capacitors 112 and 113, a smoothing resistor 114, an engine controlling revolu tion setting potentiometer 115, a resistor 116, a zener diode 117, transistors and 130, resistors 118, 121, 122, 126 and 127, capacitors 119, 124, and 139, diodes 123, 129 and 140, an arc extinguishing zener diode 131, an arc extinguishing diode 132, a feedback capacitor 133, voltage compensating Zener diodes 128 and 138, and resistors 135, 136 and 137. The resistor cutout circuit 102 comprises resistors 151, 153 and 155, transistors 152 and 156, diodes 154 and 158, an arc extinguishing diode 157, and a resistor cutout relay including a relay coil 160a, a movable contact 160/; actuated by the electromagnetic attraction of the relay coil 160a and a fixed contact 160p.

With the construction described above, the operation of this embodiment is as follows. Firstly, to start the engine, the key switch 40 is thrown to the starting terminal 40a with the result that current flows into the relay coil 190a of the starting relay 1 90 and thus the movable contact 1901) comes into contact with the fixed contact 19011 to energize the electric motor 31. Consequently, the cam switch 37 closes the contacts 33 and 34 and the cam switch 38 closes the contacts and 36. In this case, the transistor 152 in the resistor cutout circuit 102 is turned on by the base current supplied by the starting signal of the key switch 40 and thus the transistor 156 is turned off. Consequently, the movable contact 16012 of the resistor cutout relay 160 is in contact with the fixed contact 160p and thus the resistor cutout relay 160 short-circuits the control 70. Thereafter, when the key switch 40 is thrown to the operating terminal 40b, no base current is supplied to the transistor 152 of the resistor cutout circuit 102 with the result that the transistor 152 is turned off and the transistor 156 is turned on. Consequently, current flows into the relay coil 1600 of the resistor cutout relay 160 to cause the movable contact 16012 to separate from the fixed contact 160p and thereby to insert the control resistor 70 in the energizing circuit for the electric motor 31. In this operating condition, only the contacts 33 and 34 are closed by the cam switch 37. When, in this operating condition, the engine overspeeds, the cam switch 37 closes the contacts 33, 34 and 35 and the base current flows into the transistor 120. Conse quently, the relay control circuit 101 is caused to oscillate by the transistors 120 and 130, the capacitors 124 and 133 and the resistor 126 which constitute the essential elements of an astable multivibrator. Thus, the current flow to the electric motor 31 of the driving control unit 30 is controlled in accordance with the on-off ratio of the movable contacts 22b and 220 of the relay 22 in the electric motor control relay unit 20 and it is also limited by the control resistor 70. In this way, the rotational speed of the electric motor 31 is controlled. Then, when the key switch 40 is opened to stop the engine, the resistor cutout circuit 102 is also disconnected from the power source so that the movable contact 160b of the resistor cutout relay 160 comes into contact with the fixed contact 160p to short-circuit the control resistor 70. On the other hand, with the key switch 40 in the operating condition, if the direction of rotation of the diesel engine is reversed, the reversal detector 60 connects the base of the transistor 156 in the resistor cutout circuit 102 to the ground through the diode 158 to turn off the transistor 156 and thereby to shoft-circuit the control resistor 70. Accordingly, when the engine is operating, the control resistor 70 is inserted in the energizing circuit of the electric motor 31 to reduce the current flow thereto, whereas when the engine is started, stopped or reversed, the control resistor 70 is short-circuited to permit the flow of sufficicnt current to the electric motor 31. In this way, the control efficiency of the engine by the electric motor 31 is improved and any damage to the engine which may be caused by the overspeeding of the engine in operation is prevented by the operation of the resistor cutout relay 160.

The second embodiment of the present invention shown in FIG. 4 will now be described. In FIG. 4, the same reference numerals used in FIG. 3 designate the identical or equivalent parts. In other words, the second embodiment is identical with the first embodiment excepting that the resistor cutoff circuit 102 has a different circuit construction. The resistor cutout cirvcuit 102 comprises resistors 153, 161, 163, 166, 168

and 169, diodes 157, 158, 162, [164, l 6 5and 167, transistors 152 and 156, resistor cutout relay 160. During the starting period of the engine, the base current of the transistor. 156 is forcibly supplied through the diode 167 and the resistor 169 to turn the transistor 156 on. Consequently, current flows into the relay coil 160a of the resistor cutout relay 160 and thus the movable contact 160b comes into contact with the fixed contact 16021 to shortcircuit the control resistor 70. On the other hand, when the engine is operating, the base current flows into the transistor 152 through the resistor 161 so that the transistor 152 is turned on and the transistor 156 is turned off. This stops the current flow into the relay coil 160a of the resistor cutout relay 160 and the movable contact 1601; separates from the fixed contact 16011 to insert the control resistor 4 in the energizing circuit for the electric motor 31. Further, when the direction of rotation of the runningdiesel engine is reversed, the base of the transistor 152 is grounded through the diode 158 so that the transistor 152 is turned off and the transistor 156 is turned on to permit the current flow into the relay coil 16011 of the resistor cutout relay 160. Consequently, the movable contact 1601) comes into contact with the fixed contact 16011 to short-circuit the control resistor 70. Furthermore. with the engine operating, if the key switch 40 is opened to stop the engine, the connection between the contacts 33 and 34 of the switch mechanism 32 in the driving control unit 30 is maintained by the cam switch 37 for a while and the power is supplied to the resistor cutout circuit 102 through the diode 165. In this case. no base current flows into the transistor 152 so that the transis tor 152 is turned off and the transistor 156 is turned on.

'Consequcntly, the movable contact 1601) comes into Contact with the fixed contact 16011 and the control resistor is short-circuited. When the driving control unit 30 rotates the switch mechanism 32 to the normal stop position, the contacts 33 and 34 are opened to stop the supply of power to the resistor cutout control 102.

It will thus be seen that in the first embodiment of this invention shown in FIG. 1, the speed voltage corresponding to the number of revolutions of an engine is applied to the comparator zener diode 4 connected to the base of the error detecting transistor 2, the collector signal of the error detecting transistor 2 is supplied to the base of the relay actuating transistor 3 through the charging and discharging circuits comprising the capacitor 8 and the resistors 7 and 8, and a portion of the collector signal of the relay actuating transistor 3 is applied to the base of the error detecting transistor 2 through the feedback capacitor 5 and the comparator zener diode 4. Thus, there is the remarkable advantage in that when the number of revolutions of the engine exceeds the maximum normal revolutions, the error detecting transistor 2 and the relay actuating transistor 3 are caused to oscillate with the result that the ratio between the time intervals during which the movable contact 13b of the reversing transfer relay 13 engages the fixed contacts 13p and 1311, respectively, is varried in accordance with the difference between the engine revolutions and the manximum normal revolutions to vary the speed at which the control element is actuated and thereby to reliably prevent the overspeeding of the engine, and that it is possible to prevent the occurrence of hunting phenomenon of the engine and the like which may take place with the simple on-off control circuit in which the movable contact 1312 of the reversing transfer relay l3 simply comes into contact with the fixed contact 13p to move the control element in a direction that reduces the fuel injection quantity of the fuel injection pump when the number of revolutions of the engine exceeds the maximum revolutions at the normal engine speed.

Further, since the system of this invention comprises the electric motor for controlling an internal combustion engine. the control relay unit for interrupting the supply of current to the electric motor when the engine overspeeds, the control resistor inserted in the energizing circuit for the electric motor, and the resistor cutout circuit whereby the control resistor is retained in the energizing circuit for the electric motor when the engine is in operation, while the control resistor is short-circuited when the engine is started. stopped or reversed, there is the remarkable advantage in that during the operation of the engine involving the danger of the overspeeding of the engine, the current flow to the electric motor is reduced to prevent any damage to the engine due to the overspeeding of the engine and that during the starting, stopping or reversing of the engine, the supply of sufficient current to the electric motor is ensured to improve the control efficiency of the engine by the electric motor.

There is a further remarkable advantage in that by the insertion of the control resistor in the energization circuit for the electric motor, the number of operations of the control relay unit which interrupts the current supply upon occurrence of the overspeeding engine can be reduced to thereby ensure a longer life for the control relay unit.

We claim:

1. ln combination. an electric control circuit and an internal combustion engine having a fuel injection quantity control member and a rotatable member driven by said engine, said combination comprising:

means connected to said rotatable member for generating a speed voltage corresponding to the number of revolutions of said internal combustion engine, pulse generating means connected to said speed voltage generating means to start oscillating when said speed voltage exceeds a predetermined value and generate pulses having an on-off ratio which varies in accordance with said speed voltage, switch means connected 'to said pulse generating means to alternately open and close a power supply circuit in accordance with said pulses, driving means connected to said switch means for controlling said fuel injection quantity control member, to thereby increase or decrease the quantity of fuel injected in response to said opening and closing operations of said switch means. 2. An electric control circuit according to claim 1,

wherein said driving means comprises an electric motor.

3. An electric control circuit according to claim 1, wherein said switching means comprises relay means. 4. An electric control circuit according to claim 1, which further comprises a key switch having a first contact actuated during the starting period of said engine and a second contact actuated during the operating period of said engine, a resistor connected in said power supply circuit for controlling the input to said driving means. and means connected to said first and second contacts to short-circuit said resistor during said starting period and to release said short-circuiting of said resistor during said operating period.

l i l 

1. In combination, an electric control circuit and an internal combustion engine having a fuel injection quantity control member and a rotatable member driven by said engine, said combination comprising: means connected to said rotatable member for generating a speed voltage corresponding to the number of revolutions of said internal combustion engine, pulse generating means connected to said speed voltage generating means to start oscillating when said speed voltage exceeds a predetermined value and generate pulses having an onoff ratio which varies in accordance with said speed voltage, switch means connected to said pulse generating means to alternately open and close a power supply circuit in accordance with said pulses, driving means connected to said switch means for controlling said fuel injection quantity control member, to thereby increase or decrease the quantity of fuel injected in response to said opening and closing operations of said switch means.
 2. An electric control circuit according to claim 1, wherein said driving means comprises an electric motor.
 3. An electric control circuit according to claim 1, wherein said switching means comprises relay means.
 4. An electric control circuit according to claim 1, which further comprises a key switch having a first contact actuated during the starting period of said engine and a second contact actuated during the operating period of said engine, a resistor connected in said power supply circuit for controlling the input to said driving means, and means connected to said first and second contacts to short-circuit said resistor during said starting period and to release said short-circuiting of said resistor during said operating period. 